Medical Imaging

CT (CAT) Scan

The CT Scanner uses X-rays to produce an image. When you have an X-ray
of your hand, the radiation moves through your hand and onto a film
to produce an image. CT Scanners work much the same way, except instead
of film, detectors capture the radiation after it passes through your
body.

The patient moves through the gantry (circular donut shaped part of
the scanner) on a movable table. At the same time, a rotating X-ray
machine inside the gantry moves around the body. As the patient moves
through the gantry, the detectors constantly collect data as the radiation
passes through your body, and with the aid of a complex computer, a
two -dimensional image is created.

A completed scan may have as little as 20 images, such as CT of the
brain, while others have several hundred images, as is the case with
a CT of the abdomen. Each image represents a section of the body, which
can be thick (10mm) or thin (0.5mm) depending upon the body part being
examined. The CT examination is fast and painless.

The CT scanners at St. Michael's Hospital are state of the art spiral
CT and multislice scanners. Images can be viewed individually or in
rapid sequence called cini view, or reconstructed by the technologist
as a three - dimensional model which can be manipulated and rotated
to provide the physician with an optimal image for review.

Multislice CT scanners operate with greater speed, allowing advanced
CT angiography scanning. The increase in speed is an advantage for
all patients as the scan time is decreased considerably, but is most
beneficial to elderly and critically ill patients who are not able
to sustain long breath holds.